Moore, I don't see Manchester Park Rd & 511. I found 511, but that was it. Cedar Mtn Rd is visible.
How about a set of GPS coordinates for where everyone is staying, and where you camped last year. If you are going to be riding ATVs, you may have been near Hoder Recreation Reservoir, off FR 3.
GoogleEarth shows you the elevation where your cursor is, along the lower-right info ribbon of the GE window. That will give you an idea about elevation changes, if you place your cursor over a few different spots. Also, if you set your Tools>Options>Terrain Elevation Exaggeration to 1 or 2, you can drag-and-release the imagery, so it starts scrolling. While it is scrolling it almost becomes 3-D, so you can see hillsides, ravines, etc. Could be helpful in finding a place you can get your rig.
Appears to be lots of boondocking opportunities in that area, limited mostly by your rig. Good luck!
2017.5 Lance 1995
2017 F150 EcoBoost, Max Tow
Most camping off-road